1. Field of the Invention
Exemplary embodiments of the present invention relate to an oxide semiconductor thin-film transistor (TFT). More particularly, exemplary embodiments of the present invention relate to an oxide semiconductor TFT capable of preventing a reaction between an oxide semiconductor and an electrode material.
2. Discussion of the Background
Generally, a display device includes a plurality of switching elements. The switching elements include a gate electrode connected to a gate line, a semiconductor pattern insulated from the gate electrode, a source electrode connected to a data line to be electrically connected to the semiconductor pattern, and a drain electrode spaced apart from the source electrode. Examples of a TFT used as a switching element of a display device include an amorphous-silicon (a-Si) TFT, a poly-silicon (poly-Si) TFT, and an oxide semiconductor TFT.
The a-Si TFT may be uniformly formed on a large-sized substrate at low cost; however, the a-Si TFT may have low charge mobility. In contrast, the poly-Si TFT may have a higher charge mobility and lower deterioration rate of its element characteristics compared with the a-Si TFT. However, a liquid crystal display (LCD) with the poly-Si TFT may have a more complex manufacturing process than an LCD with an a-Si TFT, which may incur a larger manufacturing cost than the manufacturing cost of an LCD with an a-Si TFT.
The oxide semiconductor TFT may be manufactured using a low temperature process and may be used in a large-sized display panel. In addition, the oxide semiconductor TFT may have relatively large charge mobility. However, an oxide semiconductor may react with substituent components of a source electrode or a drain electrode such as a component metal, thereby inducing oxide semiconductor deoxidation and extraction of a cation included in the oxide semiconductor.
When the oxide semiconductor is reduced with cation extraction, the composition of a channel layer of a TFT changes so that the charge mobility of the TFT decreases. In addition, a threshold voltage temporally varies. Moreover, resistance values of wiring (i.e., gate line and data line resistances) may increase due to metal leaching from the oxide semiconductor. Thus, the TFT may not function due to metal extraction, which may lead to electrical instability and diminish reliability of the switching element.